Determination of the Apparent Isoelectric Point of the Protein Bodies of Glycine max

Abstract

With the objective of determining the apparent isoelectric point (pI) of the protein bodies of Glycine max in situ both before and after germination, seeds imbibed for 0 and 3 days were stained with methylene blue (MB) or xylene cyanol (XC) at various pH values (from 2.2 to 7.8), followed by cytophotometric measurements at λ=600 nm (MB) and λ=630 nm (XC). The results showed similar values for the protein material of cotyledon cells far from the vessels (pI=4.4±1), a progressive decrease in pI of the proteins located within the embryo after germination and pI=4.2±1 in the radicular parenchymatous cells, suggesting that for the mobilization of the reserve material there is an increase in the acidic groups of the protein bodies, which return to their initial quantity on reaching the interior of the growing cells.